1. Field of the Invention
The present invention relates to an integrated circuit (IC) card and, more particularly, to an IC card incorporating a plurality of semiconductor integrated circuit chips.
2. Description of the Prior Art
There exist a number of prior art card type portable semiconductor storage apparatuses. One such prior art storage apparatus involves a circuit board of glass-reinforced epoxy or like material containing copper wiring. The circuit board is furnished with semicondiictor integrated circuits (IC's) such as semiconductor storage and control devices, the circuits being plastic-sealed by injection molding. The semiconductor IC's are attached to the circuit board by soldering the leads of the former to the latter. The circuit board is further provided with connectors for electrical connection to an external data processing apparatus. The semiconductor IC's such as semiconductor storage and control devices as well as the circuit board are put in a suitable case for mechanical protection from the outside.
Another prior art card type portable semiconductor storage apparatus involves a circuit board mounted with bare semiconductor IC chips containing semiconductor storage and control devices and the like. Metal wires are used to connect the electrodes of the chips to the wiring layer of the circuit board (called wire bonding). The semiconductor IC chips are potted each and are furnished with connectors. The whole circuit board assembly is placed in an appropriate case.
A further prior art card type portable semiconductor storage apparatus involves a circuit board mounted with bare semiconductor IC chips havinu their projected electrodes connected to the circuit board not by wire binding but by direct alloy junction.
One disadvantage of the above-mentioned prior art IC cards is the growinla number of parts needed to attach numerous connectors and related components. The attaching of the connectors necessitates complicated assembling processes. The result is a sionificant increase in production cost.
The prior art IC card containin, plastic-sealed semiconductor storage and control devices offers higher levels of reliability and quality than the IC card containing bare-chip semiconductor storage and control devices. However, the former prior art IC card when put in a case is unfit for getting reduced in thickness.
Another problem with the prior art IC card containing plastic-sealed semiconductor storage and control devices is as follows. Because the IC's of the plastic-sealed semiconductor storage and control devices are soldered to the circuit board, reflow soldering is mandatory. During the process, the moisture contained in the plastic may evaporate under heat, causing cracks to develop in the plastic. More specifically, the plastic that seals the semiconductor IC chips has hyolroscopic property and thus contains moisture. Abrupt heating durin, the reflow soldering process causes the moisture to evaporate. The expansion resulting from the evaporation can produce cracks in the sealine plastic.
The IC card containing bare-chip semiconductor storage and control devices is more conducive to thinner card form than the IC card containing plastic-sealed semiconductor storage and control devices, but is inferior to the latter in terms of quality and reliability. That is, the potted sealing plastic tends to be brittle under partial stress concentration. Moreover, the IC card containing bare-chip semiconductor storage and control devices is basically inferior in mechanical strength to the IC card containing plastic-sealed semiconductor storage and control devices.